JP2008274423A - Fine silver particle, and process for producing fine silver particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a process for stably and efficiently producing highly dispersible fine silver particles suitable as paste components to form into a wiring material and an electrode material of an electron device. <P>SOLUTION: Regarding the process for producing fine silver particles, in a process where a reducing agent is added to a silver ion solution to reduce and precipitate silver particles, silver ions are reduced in the presence of halide ions, so as to precipitate fine silver particles. In this case, by regulating the halide concentration to the silver concentration, the particle diameter of the silver particles to be precipitated is controlled. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for stably and efficiently producing fine silver particles using a high-concentration silver ion solution, and the silver fine particles. More specifically, the present invention relates to a method for stably and efficiently producing fine, highly dispersible silver particles suitable as a paste component that becomes a wiring material or an electrode material of an electronic device, and the silver fine particles.

  In recent years, there has been a demand for miniaturization and high density of electronic devices in order to improve the functionality of electronic equipment, and in order to achieve finer wiring and electrodes, silver used as a paste material for forming them. As for the fine particles, finer and highly dispersible fine particles are required.

  Conventionally, as a method for producing silver fine particles used in electronic device materials, there is a method of obtaining silver fine particles having an average particle diameter of about several μm by reducing silver salt ammine complexes to precipitate silver fine particles, and washing and drying them. Known (Patent Documents 1 and 2). However, in this production method, it is difficult to stably obtain fine particles having an average particle size of 1 μm or less, and since the particle size distribution is wide and the particles are easy to aggregate, fine silver particles having a uniform particle size of 1 μm or less are produced. There was a problem that it was difficult.

In addition, a method is known in which silver fine particles having a small crystallite diameter are produced by reducing the silver in the pipe by joining the organic reducing agent solution in the middle of the flow path through which the silver ammine complex aqueous solution flows (patent) References 3, 4). However, in this production method, the silver ammine complex is reduced in the pipe, so that the flow path becomes narrow due to silver deposition, and the silver particles deposited on the pipe wall peel off and coarse particles are mixed. There is. In addition, in order to obtain fine silver particles, a silver ammine complex aqueous solution having a very low silver concentration is used, so that the production efficiency is low, and the yield is low because of a large loss during recovery.
JP-A-8-134513 JP-A-8-176620 JP-A-2005-48236 JP 2005-48237 A

  The present invention provides a silver fine particle that solves the above problems in the conventional production method and a production method thereof, and stably and efficiently produces fine silver particles excellent in dispersibility using a high concentration silver ion solution. A manufacturing method and silver fine particles thereof are provided.

According to this invention, the silver fine particle which solved the said subject with the following structures, and its manufacturing method are provided.
[1] Silver fine particles, wherein the silver fine particles contain a halogen in a molar ratio of 5.0 × 10 ^{−8 to} 1.5 × 10 ⁻³ with respect to silver.
[2] The silver fine particles described in [1], wherein an average particle size of 1.5 containing a halogen in a molar ratio of 5.0 × 10 ^{−8 to} 1.8 × 10 ⁻⁶ with respect to silver. ~0.5μm silver particles or silver having an average particle diameter of 0.5~0.15μm halogen is contained at a molar ratio of 1.8 × 10 ^-6 ~3.0 × 10 ^-5 with respect to silver Fine particles or silver fine particles having an average particle diameter of 0.15 to 0.08 μm in which halogen is contained in a molar ratio of 3.0 × 10 ^{−5 to} 1.5 × 10 ⁻³ with respect to silver.
[3] In a method of reducing and precipitating silver fine particles by adding a reducing agent to a silver ion solution, silver particles are precipitated by reducing silver ions in the presence of halide ions. A method for producing fine particles.
[4] The method for producing silver fine particles according to the above [3], wherein the particle diameter of the silver fine particles to be deposited is controlled by adjusting the halide concentration relative to the silver concentration.
[5] A silver nitrate solution added with aqueous ammonia as a silver ion solution, a hydroquinone solution as a reducing solution, ammonium chloride (NH ₄ Cl), ammonium bromide (NH ₄ Br), ammonium iodide as a halide ion source The method for producing silver fine particles according to [3] or [4] above, using (NH ₄ I), potassium chloride, potassium bromide, potassium iodide, sodium chloride, sodium bromide, or sodium iodide.
[6] When reducing silver ions, (i) the molar ratio of iodine to silver (I / Ag) is adjusted to 5.0 × 10 ^{−8 to} 1.8 × 10 ⁻⁶ to obtain an average particle size of 1. 5 to 0.5 μm of silver fine particles are precipitated, or (ii) the silver iodine molar ratio is adjusted to 1.8 × 10 ^{−6 to} 3.0 × 10 ⁻⁵ to obtain an average particle size of 0.5 to 0 Or (iii) adjusting the silver / iodine molar ratio to 3.0 × 10 ^{−5 to} 1.5 × 10 ⁻³ to adjust the average particle size to 0.15 to 0.08 μm. The method for producing silver fine particles according to any one of [3] to [5] above, wherein silver fine particles are precipitated.
[7] When a hydroquinone solution is added to a silver nitrate solution to which aqueous ammonia is added to reduce silver ions, the molar ratio (I / Ag) of iodine to silver is set to 5. in a silver nitrate solution having a silver concentration of 50 g / L or more. By adjusting to 0 × 10 ^{−8 to} 1.5 × 10 ⁻³ , the yield of silver fine particles having an average particle size of 1.5 to 0.08 μm is 99% or more. [3] to [6] A method for producing silver fine particles according to any one of the above.

The silver fine particles of the present invention are silver fine particles produced by reducing silver ions in the presence of halide ions, and the halogen content is 5.0 × 10 ^{−8 to} 1.5 × 10 ⁻³ with respect to silver. It is contained in a molar ratio and is a fine silver particle having fine dispersibility.

  The production method of the present invention is a method of producing fine silver particles having fine dispersibility by reducing silver ions in the presence of halide ions, and the silver fine particles can be produced stably and efficiently. According to the production method of the present invention, silver halide is preferentially produced during the reduction of silver ions, and silver crystalline primary particles are formed using the silver halide as a core, and the primary particles are aggregated to form silver fine particles. It is formed. Compared to the case where there is no halide ion, initial nuclei can be easily and reliably formed with small energy, the number of initial nuclei can be increased, and the number of primary particle aggregation centers can be increased. As a result, fine silver fine particles are stably and efficiently deposited.

  Further, according to the production method of the present invention, by adjusting the halide ion concentration with respect to the silver concentration, it is possible to control the particle diameter of the silver fine particles to be deposited. By adjusting the halogen concentration, for example, Silver particles having an average particle diameter of 1.5 to 0.5 μm, silver particles having an average particle diameter of 0.5 to 0.15 μm, silver particles having an average particle diameter of 0.15 to 0.08 μm, etc. Silver fine particles can be obtained efficiently and stably.

  Furthermore, according to the production method of the present invention, fine silver fine particles can be efficiently produced using a high concentration silver ion solution. Specifically, for example, silver fine particles having an average particle diameter of 1.5 to 0.08 μm can be obtained in a yield of 99% or more using a silver nitrate solution to which ammonia water having a silver concentration of 50 g / L or more is added. .

  In addition, since the production method of the present invention reduces silver ions in the presence of halide ions, it is only necessary to add a halide ion source together with the reducing solution, and a special apparatus that injects the reducing solution into the pipeline. Since no configuration is required, it can be easily implemented.

Hereinafter, the present invention will be specifically described together with examples.
The silver fine particles of the present invention are silver fine particles produced by reducing silver ions in the presence of halide ions, and the halide is 5.0 × 10 ^{−8 to} 1.5 × 10 ^{−3 with} respect to silver. These are silver fine particles having a fine dispersibility.

  The silver fine particles of the present invention can be produced by reducing silver ions in the presence of halide ions in a method of reducing and precipitating silver fine particles by adding a reducing agent to a silver ion solution. Moreover, in this manufacturing method, the particle diameter of the silver fine particles to precipitate can be controlled by adjusting the halide ion concentration with respect to the silver concentration.

  As the silver ion solution, a silver nitrate solution to which ammonia water is added can be used. A silver ammine complex is formed by the presence of ammonia, and silver is reduced and precipitated by adding a reducing agent.

  As the reducing solution, a solution of an organic reducing agent having a phenol group such as a hydroquinone solution, a pyrogallol solution, and a 3,4-dihydroxytoluene solution can be used. The amount of the reducing agent added is preferably such that the silver in the solution is sufficiently reduced and precipitated.

Examples of halide ion sources include ammonium chloride (NH ₄ Cl), ammonium bromide (NH ₄ Br), ammonium iodide (NH ₄ I), potassium chloride (KCl), potassium bromide (KBr), potassium iodide ( KI), sodium chloride (NaCl), sodium bromide (NaBr), sodium iodide (NaI), or the like can be used. In addition, there exists a tendency for the effect of refinement | increase to be strong in order of an iodine, a bromine, and chlorine.

  Due to the presence of halide ions, silver halide is preferentially produced during the reduction of silver ions, and silver crystalline primary particles are formed using these as nuclei. These primary particles aggregate to form silver fine particles. It is formed. Compared to the case where there is no halide ion, initial nuclei can be easily and reliably formed with small energy, the number of initial nuclei can be increased, and the number of primary particle aggregation centers can be increased. As a result, fine silver fine particles are stably and efficiently deposited.

  In the absence of halide ions, a large amount of energy is required for nucleation when silver cluster nuclei are formed by reduction of silver ions, and the number of initial nuclei is reduced because initial nuclei cannot be formed easily. Since the number of aggregation center points of the primary particles is reduced, it is difficult to obtain fine silver fine particles.

The concentration of halide ions is, for example, when a hydroquinone solution is added to a solution obtained by adding aqueous ammonia to a silver nitrate solution to reduce silver ions, the molar ratio of iodine to silver (I / Ag) is 5.0 × 10. ^-8 or more is suitable, and silver fine particles having an average particle diameter of 1.6 μm or less can be obtained. Further, the finer silver fine particles can be obtained as the molar ratio of iodine to silver is higher. Specifically, when the molar ratio of iodine to silver is 1.0 × 10 ⁻⁷ or more, for example, a silver nitrate solution having a silver concentration of 50 g / L or more is used, and the average particle diameter is 1 with a yield of 99% or more. Silver fine particles of .5 μm to 0.08 μm can be obtained.

On the other hand, when the added amount of the halide is too large, the shape of the silver fine particles is not easily formed into a spherical shape and tends to aggregate. Therefore, the molar ratio of halide ions to silver is suitably 1.5 × 10 ⁻³ or less.

  In the production method of the present invention, the particle size of the silver fine particles to be deposited can be controlled by adjusting the halogen concentration relative to the silver concentration. For example, when a hydroquinone solution is added to a silver nitrate solution to which ammonia water is added to reduce and precipitate silver ions, the molar ratio of iodine to silver (I / Ag) is adjusted as follows to obtain an average particle size of 0.08 μm. Silver fine particles of ˜1.5 μm can be obtained.

(A) The silver iodine molar ratio (I / Ag) is adjusted to 5.0 × 10 ^{−8 to} 1.8 × 10 ⁻⁶ to precipitate silver fine particles having an average particle size of 1.5 to 0.5 μm. it can.
(B) Silver fine particles having an average particle diameter of 0.5 to 0.15 μm can be precipitated by adjusting the silver iodine molar ratio to 1.8 × 10 ^{−6 to} 3.0 × 10 ⁻⁵ .
(C) The silver iodine molar ratio can be adjusted to 3.0 × 10 ^{−5 to} 1.5 × 10 ⁻³ to precipitate silver fine particles having an average particle size of 0.15 to 0.08 μm.

  The production method of the present invention is excellent in controllability of the particle diameter of the silver fine particles to be precipitated, and the particle diameter of the silver fine particles to be precipitated is an average particle diameter ± It is within the range of 10%. Moreover, the chemical solution prepared by the method of the present invention is excellent in stability over time, and the particle size change of the silver fine particles synthesized within 9 hours after the preparation is within ± 10%.

  In the production method of the present invention, halide ions are present at the time of reduction of silver ions, so the precipitated silver fine particles contain halides, but since silver ions are gradually deposited by reduction precipitation, halogens are silver fine particles. It is contained inside and therefore hardly eluted, and there is almost no influence of halogen when using silver fine particles.

  Hereinafter, the present invention will be specifically described by way of examples. The particle size was determined by calculating on the basis of the number by the laser scattering / diffraction method.

[Example 1]
A silver hydroquinone solution added with an ammonium iodide solution was added to a silver nitrate solution added with aqueous ammonia to cause silver to be reduced and precipitated. Table 1 shows the compositions of aqueous ammonia, silver nitrate solution, and hydroquinone solution. Table 2 shows the amount of ammonium iodide used and the molar ratio of iodine to silver. Table 2 shows the average particle diameter, yield, and iodine content of the precipitated silver fine particles. Further, SEM photographs of particles for some samples are shown in FIGS. In addition, the thing which does not add an ammonium iodide liquid was shown as Comparative Example 1a, and the example in which the addition amount of iodine is more than the preferred range is shown as Comparative Example 1b. Moreover, the change of the average particle diameter of silver fine particles with respect to the addition amount of iodine is shown in FIG. The upper and lower bars shown in the measured values in the figure indicate the range of variation in the measured values obtained by 10 tests.

As shown in Table 2 and FIG. 1, silver particles having an average particle size of 1.5 μm or more are precipitated in the comparative sample to which ammonium iodide is not added. However, when iodide ions are present, the silver particles become finer, and iodide ions The average particle diameter of the silver fine particles changes depending on the amount. Specifically, (i) Silver fine particles having an average particle diameter of 1.5 to 0.5 μm when the silver iodine molar ratio (I / Ag) is in the range of 5.0 × 10 ^{−8 to} 1.8 × 10 ^−6. And (ii) silver fine particles having an average particle diameter of 0.5 to 0.15 μm were precipitated when the silver-iodine molar ratio was in the range of 1.8 × 10 ^{−6 to} 3.0 × 10 ⁻⁵ , and (iii) Silver fine particles having an average particle diameter of 0.15 to 0.08 μm are deposited when the silver / iodine molar ratio is in the range of 3.0 × 10 ^{−5 to} 1.5 × 10 ⁻³ .

  Further, as shown in Table 2 and FIG. 1, the silver fine particles of the present invention have good particle size controllability, and the silver fine particles of the examples all have a mean particle size of ± 10 obtained by testing 10 times. % (Particle size control in Table 2). Furthermore, the chemical solution used in the present invention is excellent in stability over time, and the particle size of silver fine particles synthesized within 9 hours after preparation is also within a range of ± 10%.

[Example 2]
To a silver nitrate solution to which aqueous ammonia was added, a hydroquinone solution (halide mole number: 2.82 × 10 ⁻⁵ ) in which an ammonium halide solution had been added in advance was added to cause silver to be reduced and precipitated. The silver nitrate solution, hydroquinone solution, and ammonium solution shown in Table 1 were used. As shown in Table 3, NH ₄ Cl, NH ₄ Br, and NH ₄ I were used as the type of halogen. The average particle size of the precipitated silver fine particles was measured. The method for measuring the average particle diameter is the same as in Example 1. The results are shown in Table 3 and FIGS. A sample to which no ammonium halide solution was added was shown as Comparative Sample 2. As shown in Table 3 and FIGS. 7 to 10, the effect of refinement on silver particles is strong in the order of iodine, bromine, and chlorine.

Example 3
Instead of the ammonium halide solution of Example 2, silver was reduced and precipitated under the same conditions as in Example 2 except that an aqueous halide salt solution shown in Table 4 was used, and the average particle diameter of the precipitated silver fine particles was measured. The method for measuring the average particle diameter is the same as in Example 1. The results are shown in Table 4. A sample to which no aqueous halide salt solution was added was shown as Comparative Sample 3. As shown in Table 4, the effect of the present invention does not change even if the counter ion of the halide ion changes.

[Comparative Example]
Using silver nitrate solution to which ammonia water shown in Table 5 (Comparative Sample 4) and Table 6 (Comparative Sample 5) was added, hydroquinone solution was added to this solution to reduce and precipitate silver, and the average grain size of the precipitated silver fine particles The diameter was measured. The method for measuring the average particle diameter is the same as in Example 1. The results are shown in Table 7. Even when halide ions are not added to the reducing solution in advance, silver fine particles having an average particle size of 0.50 μm or less can be obtained by reducing the silver concentration. However, since the recovery is difficult, the yield is 99%. Less than

Graph showing the relationship between iodide ion addition amount and Ag particle size Graph showing the relationship between halogen type and Ag particle size Electron micrograph showing the particle state of comparative sample 1 (the length of the bottom white is 1 μm) Electron micrograph showing the particle state of Example A2 (bottom outline length is 1 μm) Electron micrograph showing the particle state of Example A5 (bottom white outline length is 1 μm) Electron micrograph showing the particle state of Example A7 (the length of the bottom white area is 1 μm) Electron micrograph showing the particle state of Comparative Sample 2 (bottom white length is 1 μm) Electron micrograph showing the particle state of Example B1 (the length of the bottom white is 1 μm) Electron micrograph showing the particle state of Example B2 (length of white at the lower end is 1 μm) Electron micrograph showing the particle state of Example B3 (length of white at the bottom is 1 μm)

Claims (7)

Silver fine particles characterized in that halogen is contained in silver fine particles in a molar ratio of 5.0 × 10 ^{−8 to} 1.5 × 10 ⁻³ with respect to silver.
2. The silver fine particles according to claim 1, wherein halogen has a mean particle diameter of 1.5 to 0.5 in which a halogen is contained in a molar ratio of 5.0 × 10 ^{−8 to} 1.8 × 10 ⁻⁶ with respect to silver. 5 μm silver fine particles, or silver fine particles having an average particle diameter of 0.5 to 0.15 μm in which halogen is contained in a molar ratio of 1.8 × 10 ^{−6 to} 3.0 × 10 ⁻⁵ with respect to silver, or Silver fine particles having an average particle diameter of 0.15 to 0.08 μm in which halogen is contained at a molar ratio of 3.0 × 10 ^{−5 to} 1.5 × 10 ⁻³ with respect to silver.
In the method of reducing and precipitating silver fine particles by adding a reducing agent to a silver ion solution, the production of silver fine particles characterized by precipitating fine silver fine particles by reducing silver ions in the presence of halide ions Method.
The method for producing silver fine particles according to claim 3, wherein the particle size of the silver fine particles to be deposited is controlled by adjusting the halide concentration relative to the silver concentration.
Aqueous ammonia silver nitrate solution was added as a silver ion solution, a hydroquinone solution as a reducing solution, ammonium chloride as a halide ion source (NH ₄ Cl), ammonium bromide (NH ₄ Br), ammonium iodide (NH ₄ The method for producing silver fine particles according to claim 3 or 4, wherein I), potassium chloride, potassium bromide, potassium iodide, sodium chloride, sodium bromide, or sodium iodide is used.
When reducing silver ions, (i) the molar ratio of iodine to silver (I / Ag) is adjusted to 5.0 × 10 ^{−8 to} 1.8 × 10 ⁻⁶ to obtain an average particle size of 1.5 to 0. Or (ii) adjusting the silver / iodine molar ratio to 1.8 × 10 ^{−6 to} 3.0 × 10 ⁻⁵ to adjust the average particle size to 0.5 to 0.15 μm. Silver fine particles are precipitated, or (iii) silver fine particles having an average particle diameter of 0.15 to 0.08 μm are prepared by adjusting the silver iodine molar ratio to 3.0 × 10 ^{−5 to} 1.5 × 10 ^−3. The method for producing silver fine particles according to any one of claims 3 to 5, wherein the silver fine particles are deposited.
When silver ion solution is reduced by adding hydroquinone solution to silver nitrate solution to which aqueous ammonia is added, the molar ratio of iodine to silver (I / Ag) is 5.0 × 10 5 in a silver nitrate solution having a silver concentration of 50 g / L or more. The yield of silver fine particles having an average particle diameter of 1.5 to 0.08 μm is 99% or more by adjusting to ^{−8 to} 1.5 × 10 ^−3. 7. A method for producing fine silver particles.